138 lines
5.3 KiB
C
138 lines
5.3 KiB
C
/****************************************************************************
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* fs/procfs/fs_procfsutil.c
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*
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* Copyright (C) 2013 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <string.h>
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#include <nuttx/fs/procfs.h>
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#if !defined(CONFIG_DISABLE_MOUNTPOINT) && defined(CONFIG_FS_PROCFS)
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#ifndef MIN
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# define MIN(a,b) ((a < b) ? a : b)
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#endif
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#ifndef MAX
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# define MAX(a,b) ((a > b) ? a : b)
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: procfs_memcpy
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*
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* Description:
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* procfs/ file data may be read by the user with different user buffer
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* sizes to receive the data. If the amount of data to be returned is
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* large or if the callers receive buffer is small, then multiple read
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* operations will be required.
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*
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* If multiple read operations are required, then each read operation will
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* be identical accept that file position (f_pos) will be incremented with
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* each read: f_pos must be incremented by the read method after each
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* read operation to provide the 'offset' for the next read.
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*
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* procfs_memcpy() is a helper function. Each read() method should
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* provide data in a local data buffer ('src' and 'srclen'). This
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* will transfer the data to the user receive buffer ('dest' and 'destlen'),
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* respecting both (1) the size of the destination buffer so that it will
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* write beyond the user receiver and (1) the file position, 'offset'.
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*
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* This function will skip over data until the under of bytes specified
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* by 'offset' have been skipped. Then it will transfer data from the
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* the procfs/ 'src' buffer into the user receive buffer. No more than
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* 'destlen' bytes will be transferred.
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*
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* Input Parameters:
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* src - The address of the intermediate procfs/ buffer containing the
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* data to be returned.
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* srclen - The number of bytes of data in the 'src' buffer
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* dest - The address of the user's receive buffer.
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* destlen - The size (in bytes) of the user's receive buffer.
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* offset - On input, this is the number of bytes to skip before returning
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* data; If bytes were skipped, this offset will be decremented.
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* Data will not be transferred until this offset decrements to
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* zero.
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*
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* Returned Value:
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* The number of bytes actually transferred into the user's receive buffer.
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*
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****************************************************************************/
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size_t procfs_memcpy(FAR const char *src, size_t srclen,
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FAR char *dest, size_t destlen,
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off_t *offset)
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{
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size_t copysize;
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size_t lnoffset;
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/* Will this line take us past the offset? */
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lnoffset = *offset;
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if (srclen < lnoffset)
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{
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/* No... decrement the offset and return without doing anything */
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*offset -= srclen;
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return 0;
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}
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/* Handle the remaining offset */
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srclen -= lnoffset;
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src += lnoffset;
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*offset = 0;
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/* Copy the line into the user destination buffer */
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copysize = MIN(srclen, destlen);
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memcpy(dest, src, copysize);
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return copysize;
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}
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#endif /* !CONFIG_DISABLE_MOUNTPOINT && CONFIG_FS_PROCFS */
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